In the related art, in an electronic timepiece, there has been adopted a method in which, in order to reduce current consumption, a plurality of normal drive pulses are prepared and one of the normal drive pulses that can be driven with a minimum energy is always selected to drive a motor. To briefly describe the selection method, a normal drive pulse is output first, and subsequently it is determined whether or not the motor has rotated. Then, when the motor has not rotated, a compensation driving pulse is output immediately to positively rotate a rotor, and the next time the normal drive pulse is output, a switch is made to output a normal drive pulse having a driving force that is one rank higher than the previous one. On the other hand, when the motor has rotated, the next time the normal drive pulse is output, the same normal drive pulse as the previous one is output. Then, the normal drive pulse is selected by a method in which, when the same driving pulse is output a predetermined number of times, a switch is made to a normal drive pulse having a driving force that is lower by one rank.
Note that, as the related-art method of detecting whether or not the rotor has rotated, there has often been used a method in which, after finishing application of the normal drive pulse, a rotation detection pulse is output to steeply change an impedance value of a coil of a stepping motor, and an induced voltage generated in the coil is detected across coil terminals to make a rotation determination based on a free vibration pattern of a rotor. For example, one of two drive inverters respectively connected to both ends of a coil is first operated in a first detection mode to output a rotation detection pulse, and the first detection mode is stopped when a rotation detection signal occurs. Meanwhile, another drive inverter is operated in a second detection mode to output a rotation detection pulse, and a rotation success is determined when a rotation detection signal occurs in the second detection mode.
In the second detection mode, it is detected that the rotation has been successful, that is, a rotor has exceeded a peak of a magnetic potential. The detection in the first detection mode before the second detection mode is conducted in order to prevent detection of an erroneous detection signal that may occur before the rotor has completely exceeded the peak of the magnetic potential in a case of being driven relatively weakly, and in order to prevent the detection signal from being erroneously detected as a signal that has exceeded the magnetic potential even before the rotation of the rotor has been finished. Therefore, a technology for conducting first detection mode before the second detection mode is known to be effective for conducting rotation detection more positively (see, for example, Patent Literature 1, Patent Literature 2, and Patent Literature 3).
Note that, in Patent Literature 4, as the method of changing the driving force of the normal drive pulse, there is described a method in which a driving pulse is composed of a plurality of subpulses (hereinafter referred to as “choppers”), and duties of the subpulses (choppers) are controlled to change pulse widths. Note that, such a driving pulse is hereinafter referred to as “chopper driving pulse”.